This invention relates to a multi-layer article having a fluoroelastomer layer and a barrier layer, and a method of making the multi-layer article.
Fluorine-containing polymers (also known as xe2x80x9cfluoropolymersxe2x80x9d) are a commercially useful class of materials. Fluoropolymers include, for example, crosslinked fluoroelastomers and semi-crystalline or glassy fluoropolymers. Fluoropolymers are generally of high thermal stability and are particularly useful at high temperatures. They may also exhibit extreme toughness and flexibility at very low temperatures. Many of these fluoropolymers are almost totally insoluble in a wide variety of solvents and are generally chemically resistant. Some have extremely low dielectric loss and high dielectric strength, and may have unique non-adhesive and low friction properties. Fluoroelastomers, particularly the copolymers of vinylidene fluoride with other ethylenically unsaturated halogenated monomers such as hexafluoropropylene, have particular utility in high temperature applications such as seals, gaskets, and linings.
Multi-layer constructions containing a fluoropolymer enjoy wide industrial application. Such constructions find utility, for example, in fuel line hoses and related containers and hoses or gaskets in the chemical processing field. Adhesion between the layers of a multi-layered article may need to meet various performance standards depending on the use of the finished article. However, it is often difficult to establish high bond strengths when one or more of the layers is a fluoropolymer, in part, because of the non-adhesive qualities of fluoropolymers. Various methods have been proposed to address this problem. One approach is to use an adhesive layer or tie layer between the fluoropolymer layer and the second polymer layer. Surface treatments for the fluoropolymer layer, including the use of powerful reducing agents (e.g., sodium naphthalide) and corona discharge, have also been employed to enhance adhesion. In the case of fluoropolymers containing interpolymerized units derived from vinylidene fluoride, exposure of the fluoropolymer to a dehydrofluorinating agent such as a base has been used, as well as polyamine reagents applied to the fluoropolymer surface or incorporated within the fluoropolymer itself. A need still exists for simple, effective means to bond to fluoropolymer containing materials, particularly in a multi-layer constructions.
In one aspect, a multi-layer article includes a first polymer layer, a substrate, and a bonding layer on a surface of the first polymer layer and in contact with the substrate. The first polymer layer includes a fluoropolymer. The fluoropolymer can be a fluoroplastic. The bonding layer includes a fluoroelastomer, wherein the fluoroelastomer comprises a monomer segment derived from an olefinic hydrocarbon.
In another aspect, a process for preparing a multi-layer article includes providing a first polymer layer, providing a substrate, providing a bonding layer on a surface of the first polymer layer and in contact with the substrate, and heating the first polymer layer and the bonding layer. The first polymer layer includes a fluoropolymer. The bonding layer includes a fluoroelastomer.
The fluoroelastomer can be a copolymer. In addition to the olefinic hydrocarbon monomer, the copolymer can be derived from fluorinated monomers including, for example, tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, fluorinated vinyl ethers or combinations thereof. The olefinic hydrocarbon can be propylene or ethylene. The bonding layer can include an adhesion promoter, an amino silane, an aldimine silane or a ketimine silane.
The substrate can include a metal or a non-fluorinated polymer, such as a thermoplastic polymer or a thermoplastic elastomer. The non-fluorinated polymer can be a nitrile rubber, an ethylene-propylene-diene monomer rubber, an epichlorohydrin rubber, an ethylene-acrylate copolymer rubber, a polyamide, a polyurethane, a polyolefin, or combinations thereof.
In another aspect, a multi-layer article includes a first polymer layer, a substrate, and a bonding layer on a surface of the first polymer layer and in contact with the substrate. The first polymer layer includes a fluoroplastic. The substrate can include a non-fluorinated polymer, a fluoropolymer, or a metal. The bonding layer includes an adhesion promoter and a fluoroelastomer derived from at least a fluorinated monomer and an olefinic hydrocarbon.
The bonding layer fluoroelastomer provides not only excellent adhesion to the fluoropolymer and substrates, but can also improve sealing of connector parts, joints or gaskets and can increase the amount of force needed to separate the fluoroplastic inner layer and connector parts or joints.
Improved adhesion between a fluoropolymer layer and a second layer can arise from coating the fluoropolymer layer and/or the second layer with a fluoroelastomer solution. Fluoroelastomer solution can provide excellent adhesion between the fluoropolymers and substrates such as metal and can improve the sealing from connector parts or joints or gaskets. Excellent interlayer adhesion of fluorine-containing polymer such as copolymer of ethylene and tetrafluoroethylene (ETFE) and a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (THV) to metallic substrates such as stainless steel can be obtained. The multi-layer compositions can have unexpected improved interlayer adhesion and sealing or pull-off force between the fluoroplastic inner layer and connector parts.
Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.